Reference for Medical Students, by Medical Students

Life in the eFAST Lane: extended Focused Assessment with Sonography for Trauma (Part 2)

We’re back! Last time we reviewed eFAST basics and part of the eFAST technique. Hopefully you’ve been practicing the heart, RUQ, and LUQ scans like my friend below. So without further adieu…. I give you eFAST Part Deux!

Place the probe just above the pubic symphysis and look for the bladder in men and both the bladder and uterus in women

If it doesn’t feel a little awkward, you’re not low enough

Once you’ve finished the longitudinal view, turn the probe 90° to get the transverse view. Both views should be evaluated to avoid false positives

Figure 2 – Longitudinal probe position(from sonocloud.org)

Figure 3 – Good transverse probe position

Figure 4 – poor transverse probe position (note the angle of the probe)

The Technique

Scan through the entire bladder

Be sure your probe is perpendicular to the patient when scanning. Do not crank the probe to extreme angles to find the bladder.

If you’re not seeing bladder with the probe perpendicular to the patient, slide it down or up in a plane parallel to the patient. This is important to avoid false positives or false negatives to due changing the angle of the pelvis image.

The image (in men):

Find the bladder. The rectovesicular pouch (between rectum and bladder) is immediately posterior to the bladder.

Now find the prostate (inferior to the bladder) and scan towards the patient’s head until it disappears. This marks the beginning of the rectovesicular pouch.

The prostate is an extra-peritoneal organ. It marks the inferior end of the rectovesicular pouch.

Scan the rectovesicular space until the bladder disappears

The image (in women)

Find the uterus (posterior to the bladder). The pouch of Douglas (rectouterine pouch) is immediately behind it.

Scan the pouch of Douglas until the uterus and bladder disappear

Interpretation:

A positive exam has free fluid

In both men and women this is the 1st place blood collects in the lower abdomen

In men: look for free fluid in the rectovesicular pouch (behind the bladder)

In women: look for free fluid in the pouch of Douglas

Be aware of the possibility of false positives if your probe angle is too steep in the transverse plane

When your probe angle is too steep, you change the viewing plane so that images that appear posterior to the bladder on the screen are actually more inferior and extraperitoneal. This means you’re imaging more inferior structures (like seminal vesicles, which contain fluid… can we say false positive) and missing the peritoneal space you should be evaluating.

Discussion of Relevant Anatomy: The Brains Behind an eFAST (Continued from Part 1)

In the pelvic view, anatomy is exceptionally relevant to understanding an eFAST exam. The borders of the peritoneal and pelvic compartment meet here. It’s important to know where the compartment boundaries are, so you can identify which compartment free fluid originated from. The pelvis is also an important dependent area. This is a hot spot for finding free fluid, so pay attention to the pelvis.

In men, you are looking for free fluid in the rectovesicular pouch. This is between the rectum and bladder. Both of these are extra-peritoneal structures, but they are draped in peritoneum superiorly and along the surfaces between them. The space between them is in the peritoneal cavity, so any fluid in the rectovesicular pouch is intra-abdominal free fluid. The inferior border of the rectovesicular pouch can be identified by the prostate, which is an extraperitoneal structure just inferior to the bladder and adjacent to the inferior border of the rectovesicular pouch. Another extraperitoneal structure to consider are the seminal vesicles, which are posterior to the inferior portion of the bladder and inferior to the rectovesicular space. Since seminal vesicles contain fluid, this fluid could be falsely identified as intra-peritoneal with improper probe positioning. Seeing seminal vesicles like this is uncommon, but definitely possible. More common would be an extraperitoneal bladder rupture that you could diagnose this way, which would be treated differently than an intraperitoneal rupture.

It’s important to know if you’re extraperitoneal vs. intraperitoneal. This is why keeping the probe perpendicular to the patient is so important. If you mistakenly cranked the probe in the transverse view and imaged the bladder at an angle, images that appear posterior to the bladder on your screen would actually be more inferior (see figure 13 below). This would reveal extraperitoneal structures instead of the peritoneum. It’s an easy enough mistake, so be aware of it

Figure 13 – Male Pelvic Anatomy in Ultrasound: note the different viewing planes of each probe angle and the structures they visualize

Scanning in two planes (longitudinal and transverse) also minimizes false positives and false negatives, since the longitudinal view can help determine whether fluid is more superior in the rectovesicular pouch or more inferior in an extraperitoneal structure. So basically, in men scan the entire bladder to visualize the entire rectovesicular space and be aware of your probe angle, so you don’t mistake extraperitoneal fluid for intra-abdominal fluid (a false positive) or miss intra-abdominal fluid (a false negative). Now for the ladies.

In women, you are looking for free fluid in the pouch of Douglas, the space between the uterus and the rectum. When you’re scanning the pelvis, you’ll see bladder most anteriorly, then uterus, and finally rectum. The uterus and rectum have the same peritoneal cover as in men, so the pouch of Douglas is in the peritoneum and free fluid found in it originated from the abdomen. And that’s it for pelvic anatomy.

The last scan is the lungs. Here you’re checking for pneumothorax using features of the pleural line and other chest anatomy. The visceral and parietal pleura come together with a little bit of fluid to hold them together just below the ribs. If the pleura are sliding over one another, no pneumothorax is present. A sliding pleural line looks shimmery or like “ants marching in a line.” Be sure to hold your probe still when evaluating the pleural line, so there’s no illusion of movement caused by a shifting image on the screen. If there is no sliding, you’ll still see a pleural line from the parietal pleura. It just won’t be shimmery or move.

Another feature of intact pleura are B-lines. These look like comet tails radiating down from the pleural line into the lung. They’re caused by fluid and air interfaces distorting the sound waves. If there’s fluid, there’s no pneumothorax. So B-lines rule out pneumothorax! And since air tends to rise, duh, you should evaluate for pneumothorax at the highest point of the chest for each lung. It’s like reverse dependence. And that, ladies and gentlemen, concludes our tour of eFAST anatomy.

But let’s face it… these probably aren’t as emergent as the raging hemorrhage into the abdomen cases anyways

Too much fat is bad. It’s bad for the patient and bad for ultrasound. Getting good images on an obese patient is hard! Be aware of this! (Personally, I troll the ER for obese trauma patients and re-eFAST them, so I’ll be better at obese patient ultrasound when there’s an emergency and it really counts.)

Patients are people and they’re generally scared. You will be close to the patient’s head during an eFAST. Don’t be caught off guard if a scared trauma patient looks to you for information or comfort because you’re so close. This is a little obvious, but as a student sometimes we forget these things. The first time this happened to me a trauma patient (that I thought was obtunded) opened his eyes and grabbed my arm. I jumped so hard it was like he shocked me. He was scared and asking if he was paralyzed. It took me a second to get my wits together enough to tell him that moving his arms and legs was a good sign. Just be aware that if you’re doing an eFAST on a trauma patient, you may be the closest person the patient can talk to. Be nice.

The eFAST is a great ultrasound exam. It’s faster than other imaging and can be done in just a few minutes (a huge plus for the hemodynamically unstable patient). It can be performed at the bedside without interrupting ongoing medical care. There’s no radiation, unlike CT or x-ray. It’s sensitive, specific, and accurate. And it’s a superior diagnostic tool for a number of conditions, like pneumothorax and hemothorax. eFAST ultrasounds save lives! The scan consists of a RUQ, LUQ, pelvic, cardiac, and lung ultrasound. And to top it all off, it’s not hard to learn. I promise! This is a foundational ultrasound exam in emergency medicine and should be a part of any physician’s physical exam skills. Now go practice some eFASTs! And be sure to check out the Quick Hit post for all the info from parts 1 and 2 in summary form!

Other Resources

Here are some extra eFAST resources. I highly recommend the Ultrasound Podcast if you want to learn more about ultrasound!